The proposed study will investigate the role of self-control in smoking cessation and whether interventions that improve self-control can help reduce the risk of lapsing among smokers who wish to quit. Quitting smoking takes self-control, as the craving for nicotine and the habit of smoking must be overridden. Such self-control is difficult and often fails, despite the best intentions of the individual. A new theory of self-control may help explain why and when self-control is likely to fail as well as provide a possible intervention that may improve self-control in the long-term. According to this theory, self-control performance depends a limited resource (self-control strenqth). Individuals higher in self-control strength perform better on measures of self-control than individuals lower in self-control strength. This strength is consumed (depleted) as the individual exerts self-control. Thus, in the short-term, exerting self-control should result in poorer self-control performance. Individuals trying to quit smoking should be more likely to lapse on days when they have many self-control demands than on days when they have fewer self-control demands. In the long run, exerting self-control should have the opposite effect. The theory predicts that practicing of self-control should lead to a building of strength and an improvement in self-control. Like physical exercise, exerting self-control leads to weakness and poorer performance in the short-term, but increased strength and better performance in the long-term. Prior studies have found evidence that practicing self-control leads to an improvement in self-control. We predict that smokers who practice self-control prior to quitting should be more likely to succeed in their cessation attempt than smokers who do not practice self-control. The present research can help advance our knowledge of both the short and long-term effects of exerting self-control on smoking cessation. This is important to understanding the self-control processes that underlie abstaining from cigarettes as well as changing other health behaviors. Information from this study will increase our comprehension of self-control and the regulation of smoking, which may be useful in the design of smoking cessation programs.